Lars J. Björklund

Manual Ventilation with a Few Large Breaths at Birth Compromises the Therapeutic Effect of Subsequent Surfactant Replacement in Immature Lambs

The reason why some infants with respiratory distress syndrome fail to respond to surfactant, or respond only transiently, is incompletely understood. We hypothesized that resuscitation with large breaths at birth might damage the lungs and blunt the effect of surfactant. Five pairs of lamb siblings were delivered by cesarean section at 127-128 d of gestation. One lamb in each pair was randomly selected to receive six manual inflations of 35-40 mL/kg (“bagging”) before the start of mechanical ventilation, a volume roughly corresponding to the inspiratory capacity of lamb lungs after prophylactic surfactant supplementation. Both siblings were given rescue porcine surfactant, 200 mg/kg, at 30 min of age. Blood gases and deflation pressure-volume (P-V) curves of the respiratory system were recorded until the lambs were killed at 4 h. The P-V curves became steeper after surfactant in the control group, but no such effect was seen in those subjected to bagging. At 4 h, inspiratory capacity and maximal deflation compliance were almost three times higher (p < 0.01) in the controls than in the bagged lambs. The latter were also more difficult to ventilate and tended to have less well expanded alveoli and more widespread lung injury in histologic sections. We conclude that a few inflations with volumes that are probably harmless in other circumstances might, when forced into the surfactant-deficient lung immediately at birth, compromise the effect of subsequent surfactant rescue treatment. Our findings challenge current neonatal resuscitation practice of rapidly establishing a normal lung volume by vigorous manual ventilation.

Lung recruitment at birth does not improve lung function in immature lambs receiving surfactant

Background: In mature animals with surfactant deficiency induced by lung lavage, the therapeutic effect of exogenous surfactant is enhanced by a lung recruitment maneuver. We then tested whether a lung recruitment maneuver at birth immediately before surfactant treatment would improve lung function also in preterm lambs with surfactant deficiency due to immaturity.

Islet antibodies and remaining beta-cell function 8 years after diagnosis of diabetes in young adults : a prospective follow-up of the nationwide Diabetes Incidence Study in Sweden.

Objectives.  To establish the prevalence of remaining β‐cell function 8 years after diagnosis of diabetes in young adults and relate the findings to islet antibodies at diagnosis and 8 years later.

Lung volumes and pressure-volume relations of the respiratory system in small ventilated neonates with severe respiratory distress syndrome

Total lung capacity (TLC), inspiratory capacity (IC), functional residual capacity (FRC), and deflation pressure-volume (P-V) curves were studied in 16 intubated neonates (540-3300 g), 10 with severe respiratory distress syndrome(RDS) and 6 air-ventilated with normal chest radiograms. FRC was measured using washout of a tracer gas (sulfur hexafluoride), and TLC and IC were calculated after inflating the lungs to 30 cm H2O. P-V curves were obtained during expiration from TLC using an interrupter technique, and the steepest slope of the curve, i.e. the maximum compliance(Crs-max), was calculated. In addition, an index of ventilation inhomogeneity (pulmonary clearance delay, PCD) was computed from the shape of the SF6 washout curve. TLC/body weight was less in the RDS group than in the air-ventilated group (median 19 and range 16-43 mL/kg versus 48 and 43-52 mL/kg, respectively; p < 0.01), mainly because of a marked reduction in IC (median 11 and range 8-24 mL/kg versus 29 and 28-40 mL/kg; p < 0.01). The flatter P-V curve in the RDS group was reflected also in a lower Crs-max (median 0.7 and range 0.4-1.7 cm H2O-1 kg-1) than in the air-ventilated group (2.3 and 2.0-3.1 mL cm H2O-1 kg-1, respectively; p < 0.01). Thus, there was no overlap in IC or Crs-max between the groups, suggesting that reductions in these measures may be main characteristics of RDS. On the other hand, no difference in PCD was found, indicating that, in infants with RDS, the tidal volume is distributed fairly homogeneously to the ventilated parts of the lungs.

The pressure at the lower inflexion point has no relation to airway collapse in surfactant-treated premature lambs.

Background: The lower inflexion point (LIP) on the inspiratory part of the pressure–volume (PV) loop has been suggested to be related to the pressure at which air spaces collapse. Our hypothesis is that airway collapse might instead be assessed from the upper inflexion point on the expiratory part of the PV‐loop (UIPexp), where lung volume starts to decrease significantly. We therefore examined whether there was a relation between LIP and UIPexp in premature surfactant‐treated lambs.

Airway and body surface sensors for triggering in neonatal ventilation

Failure of neonatal patient triggered ventilation may reflect a delay in delivery of flow relative to the inspiratory effort of the infant. Transmission of diaphragmatic contraction to the sensor site (patient delay) and further transmission to and within the sensing device (device delay) both contribute to the delay in triggering. Patient and device delays were studied for different sensing systems in 36 infants, 24 of whom were intubated. Device delay was long (<40 ms) with a conventional apnoea monitor compared with sensors placed at the airway opening (2 ms), the inspiratory (12 ms) and expiratory (3 ms) pressure transducers of the ventilator, the Graseby capsule (8 ms), strain gauges (3 ms) and oesophageal pressure (6 ms). In near normal infants, the sum of patient and device delays for the latter sensors was less than 20 ms and a minor component of the total delay. However, in severe lung disease the total delay may be more than 100ms even for airway sensors.

Earlier Apgar Score Increase in Severely Depressed Term Infants Cared for in Swedish Level III Units With 40% Oxygen Versus 100% Oxygen Resuscitation Strategies: A Population-Based Register Study

OBJECTIVES. The aim of this study was to evaluate whether a resuscitation strategy based on administration of 40% oxygen influences mortality rates and rates of improvement in 5-minute Apgar scores, compared with a strategy based on 100% oxygen administration. METHODS. A population-based study evaluated data from 4 Swedish perinatal level III centers during the period of 1998 to 2003. During this period, the centers used either of 2 resuscitation strategies (initial oxygen administration of 40% or 100%). Live-born, singleton, term infants with 1-minute Apgar scores of <4, with a birth weight appropriate for gestational age, and without major malformations were included in the study (n = 1223). RESULTS. Infants born in hospitals using a 40% oxygen strategy had a more rapid Apgar score increase than did infants born in hospitals using a 100% oxygen strategy; however, no difference remained at 10 minutes. The mean Apgar score increased from 2.01 at 1 minute to 6.74 at 5 minutes in the 2 hospitals initiating resuscitation with 40% oxygen, compared with 2.01 to 6.38 in the 2 hospitals using 100% oxygen, with a mean difference in Apgar score increases of 0.36. At 5 minutes, 44.3% of infants born in the hospitals using 100% oxygen had an Apgar score of <7, compared with 34.0% of infants at the hospitals using 40% oxygen. At 10 minutes, the mean Apgar scores were 8.16 at the hospitals using 40% oxygen and 8.07 at the hospitals using 100% oxygen. There were no significant differences in rates of neonatal death, hypoxic ischemic encephalopathy, or seizures in relation to the 2 oxygen strategies. CONCLUSION. Severely depressed term infants born in hospitals initiating resuscitation with 40% oxygen had earlier Apgar score recovery than did infants born in hospitals using a 100% oxygen strategy.

Massive feto-maternal hemorrhage : Diagnosis by cardiotocography, doppler ultrasonography and ST waveform analysis of fetal electrocardiography

A 34-year-old healthy gravida 2 para 1 presented after an uncomplicated pregnancy at term with a 2-day history of diminished fetal movements. Fetal anemia was suspected by fetal heart rate monitoring and Doppler estimation of the fetal peak blood flow velocity of the middle cerebral artery. We were also fortunate to register pathological ST waveform changes of the fetal ECG indicating fetal hypoxia. The diagnosis of a massive feto-maternal hemorrhage was confirmed by an extremely high fraction of erythrocytes containing fetal hemoglobin in maternal blood and, after delivery, by placental histology.

Changing trend in perinatal management and outcome of extremely low birthweight (ELBW) infants

Perinatal care of the extremely preterm and low birthweight (ELBW) infant is founded on basic principles of physiology and knowledge about the prevailing pathophysiological mechanisms. New therapies in clinical care are usually introduced non‐uniformly, so more often there is a gradual rather than a sudden change in the development of perinatal care, conceivably involving also an important learning process. This was confirmed in an evaluation of respiratory care for ELBW infants (n = 325) over a 9‐year period (1986–1994). Although birthweight (mean 815 g) and degree of immaturity at birth (mean 26.7 weeks of gestation) did not change over the years, our trend analysis showed that the survival rate increased from 47% to 70% (p < 0.04) and the percentage of survivors without bronchopulmonary dysplasia and/or major intracranial haemorrhages (ICH grades 3 and 4) increased from 67% to 87% (p < 0.006). We suggest that besides medical treatment per se, refinement and tuning of nursing and medical care procedures will also affect the total outcome of ELBW infants.

Lung mechanics (FRC and static pressure-volume diagram) after endotracheal surfactant instillation : preliminary observations

Preliminary measurements of functional residual capacity (FRC) with the sulphurhexafluoride technique and static pressure volume diagrams were performed in newborn infants with respiratory distress syndrome receiving endotracheal instillation of natural porcine surfactant (Curosurf, 100 or 200 mg/kg). Within the first hour after surfactant treatment there was an increase in FRC and distensibility of the lungs persisting for 24-48 h.